This invention relates generally to electric motors and more particularly, to bearing load washer for an electric motor.
Known electric motors typically include a motor housing, a stator, and a rotor assembly. The rotor assembly includes a rotor core and a rotor shaft extending through the core. The housing includes a shell and two endshields and houses at least a portion of the rotor assembly. Electric motors also include at least one bearing sized to receive the rotor shaft. Typically the bearings are positioned in endshield bearing pockets. The endshields attach to ends of the housing shell. For optimum operation of the motor, the bearings need to align with the rotor shaft, i.e., the center of the bearing cartridge opening needs to align with the centerline of the rotor shaft.
Usually a load washer is located in the endshield bearing pocket. The load washer is positioned to seat against the bearing outer race. Typically the load washer is sized to loose fit in the endshield bearing pocket to allow radial/diametrical growth when the washer is compressed. If a loose fit is not provided, the washer can pack down into the bearing pocket and not return to its natural seat against the outer race of the bearing. However, during an assembly process with the motor shaft in a vertical downward position and the load washer in the top endshield bearing pocket, a loose fit load washer falls out of the endshield producing an assembly defect.
It would be desirable to assemble electric motors in a vertical shaft down mode with the load washer in the top endshield pocket and not have the washer fall out of the endshield during assembly.
A bearing load washer in an exemplary embodiment of the present invention permits assembly of electric motors with the rotor shaft in a vertical position and extending downward. The bearing load washer includes a plurality of portions that form a non-planar, substantially circular shaped, washer body. The plurality of portions form a wave pattern. This wave shaped washer is sometimes referred to as a wave washer.
The washer body includes a center opening sized so that an electric motor rotor shaft can extend through the opening. The washer body includes an outer circumferential surface and at least one raised area extending radially from the outer circumferential surface. The raised areas are configured to increase the outside diameter of the washer so that the outer circumferential surface engages the inner surface of an endshield bearing pocket at each raised area of the outer circumferential surface. The engagement of the outer surface raised areas with the inner surface of the endshield bearing pocket permits the endshield to be turned upside down with the bearing washer remaining in the bearing pocket of the endshield. Because the bearing washer only engages the inner surface of the bearing pocket at the raised portions, there is still room between the outer surface of the washer and the inner surface of the bearing pocket to permit radial/diametrical growth when the washer is compressed.
The above described bearing load washer permits assembly of an electric motor in a vertical, downward extending shaft position. Particularly, a first endshield is positioned in a motor assembly fixture. Then a rotor core and rotor shaft subassembly with bearings at each end is positioned in the assembly fixture with the rotor shaft extending downward through the endshield and one bearing assembly positioned in the endshield bearing pocket. Next a stator and motor housing subassembly is positioned so that the rotor core extends through a stator bore and the housing engages the first endshield. Then the above described bearing load washer is positioned in the bearing pocket of a second endshield with the raised areas of the outer surface of the washer engaging the inner surface of the bearing pocket. The endshield and bearing washer assembly is inverted and then positioned on the motor so that the endshield engages the motor housing and the second bearing assembly is received in the bearing pocket of the second end shield with the bearing load washer engaging the outer race of the bearing. The endshields are then attached to the motor housing with bolts.
The above described bearing load washer permits assembly of an electric motor in a vertical, downward extending shaft position without the bearing load washer falling from the endshield. The raised areas of the outer circumferential surface of the washer provide a light press fit retention in the endshield bearing pocket without interfering with the function of the load washer.